These High-Speed Flexible Circuits Can Drive Micro-LED Displays or High-Resolution Touch Sensors

Researchers from Stanford University have made a breakthrough in compact, stretchable electronics for wearable and implantable devices — delivering skin-like integrated circuits five time smaller than their predecessors but operating three orders of magnitude faster.

"We've made a significant leap forward. For the first time, stretchable integrated circuits are now small enough and fast enough for many applications," claims Zhenan Bao, a K. K. Lee Professor in Chemical Engineering at Stanford and the paper's senior author, of the team's work. "We hope that this can make wearable sensors and implantable neural and gut probes more sensitive, operate more sensors, and potentially consume less power."

The circuits developed by the team are made from carbon nanotubes and soft elastic materials built in a fishnet-like structure, capable of continuing to operate even as they're stretched and folded. By sandwiching multiple layers together, the team has been able to break through size and performance limitations hindering commercialization of its previous work.

In one demonstration of the new circuits, the team built a matrix of more than 2,500 sensors offering a tenfold increase in sensitivity over the human fingertip — and capable of recognizing Braille. "With Braille, you usually sense one letter at a time," explains co-first author Donglai Zhong. "With such a high resolution, you could sense a whole word, or potentially a whole sentence, with just one touch."

A second demonstration showed off the increased performance by driving a micro-LED display at a 60Hz refresh rate, a speed the team's previous circuits couldn't handle. "Preliminary results demonstrate that our transistor can be used to drive commercial displays commonly used in computer monitors," says Can Wu, co-first author. "And for biomedical applications, a high-density, soft, and conformable sensing array could allow us to sense human body signals, such as from our brains and muscles, at a large scale and fine resolution. This could lead to next-generation brain-machine interfaces that are both high-performance and biocompatible."

"There are still challenges for the future of this technology, but these recent developments open up some very exciting biomedical applications for wearable and implantable electronics," adds Bao in conclusion. "And it also has applications in soft robotics, giving robots a sensing functionality that approaches that of humans and makes them safer for people to work with."

The team's work has been published under closed-access terms in the journal Nature.

Main article image courtesy of Donglai Zhong, Jiancheng Lai, and Yuya Nishio/Stanford University.